Operation Hardtack II

Operation Hardtack II
Hardtack II Sanford, 4.9 kilotons.
Information
Country	United States
Test site	NTS Area 12, Rainier Mesa NTS Areas 5, 11, Frenchman Flat NTS, Areas 1–4, 6–10, Yucca Flat
Period	1958
Number of tests	37
Test type	balloon, dry surface, tower, underground shaft, tunnel
Max. yield	22 kilotonnes of TNT (92 TJ)
Test series chronology
← Operation Argus Operation Nougat →

Operation Hardtack II^[1] was a series of 37 nuclear tests conducted by the United States in 1958 at the Nevada Test Site. These tests followed the Operation Argus series and preceded the Operation Nougat series.

With test moratoriums on the horizon, American weapons labs rushed out many new designs. A hard deadline for testing was set at midnight (0000 hrs), October 31, 1958, as negotiations were set to start that day, and the schedule shows it, with 29 tests executed in October, four of them on the last day. One other test was cancelled because weather delays postponed it across the midnight deadline. After the conclusion of Hardtack II, the United States announced a unilateral testing moratorium, which the Soviet Union joined after two last tests on November 1 and 3.^[2] In September 1961, the Soviet Union resumed nuclear testing — including the test of the most powerful nuclear device ever designed, the Tsar Bomba, in October — and the United States followed suit with Operation Nougat.